Damaged ring gear on flywheel

[ianc]

This is the first time i’ve posted on here and wonder if anyone can help?

Apologies this may be a bit long

In Nov 21 I bought a 1965 Cooper S. It hadn’t been driven since 1998 and was garaged. The previous owner said the clutch had failed and had started to dismantle all the ancillaries to remove the engine and then fell into bad health and there it sat

I took it to a mini specialist who put the engine back together. In the process of replacing the clutch I had a stainless steel flywheel fitted (MED ST1). The original starter motor was refitted.

After a week or so the starter motor started to fail so I replaced it. The starter is an inertia type and before fitting I checked that the number of teeth matched the original starter. This solved the starting issue.

Fast forward to Feb 22 and probably about 500 miles driven, I took it to a restorer for a bare metal respray, which involved removing the engine.

Once the engine was back in the restorer went to re install the starter motor, but before doing so inspected (as best he could) in the clutch housing. He noticed the ring gear on the flywheel seemed damaged. He then also tested the new starter motor I had fitted and found it no longer worked!

This is so strange as I drove the car to the restorer, it had started and driven perfectly on the way there. I don’t believe the restorer caused the damage, they’re very reputable and experienced and I trust them.

Could anyone shed any light on why this may have happened after only driving so few miles on a new flywheel and starter motor?

Thanks in advance

[mk1]

Hi Ianc, Welcome to the forum.

I think I may know why you have suffered this issue.

There are two sorts of flywheel & starter that both look very similar & are very difficult to tell apart, whilst the two will work when not matched it will cause the sort of damage you describe.

The two types are as follows:

Inertia starter & flywheel.
These were the standard fitment from 1959 until the 1980's or so. Someone who is better at later change points will be able to tell you exactly when.

Pre engaged starter & Flywheel.
These came in towards the end of Mini production & work MUCH better than the original inertia jobby.

Most steel flywheels that are supplied go into competition & fast road cars where easy starting is important so pre engaged starter flywheels are now more popular. Where as there is a lot less demand for an inertia starter steel flywheel.

I feel sure that you have an inertia starter & a pre-engaged flywheel.

As long as the flywheel is not too damaged, I would swap starters for the later pre-engaged model, but if the original look is important to you, it may be worth thinking about swapping the pre engaged flywheel for the correct inertia one.

Either way, you need to make sure that both parts are matched correctly.

Here are a few links to help.

Inertia Flywheel:
http://www.minispares.com/product/Class ... o%20search

Pre-engaged Flywheel:
http://www.minispares.com/product/Class ... o%20search

Inertia Starter:
http://www.minispares.com/product/Class ... o%20search

Pre-engaged Starter:
http://www.minispares.com/product/Class ... o%20search

There are other options too, but this gives you some idea of what I am on about.

Having just read this on the Minispares web site, it may also be worth bearing in mind.
"Do not fit the 10 tooth starter sold by many as it can ruin the ringear or the bendix. Other leyland cars used 10 teeth such as Sprite, Spitfire and Mini Metro and often get fitted ass they are cheaper but 9 teeth is rarer to buy but is meant for Mini 107 teeth ringears.

[ianc]

Mark

Thank you for such a swift response. So the likelihood is that I’ve fitted the wrong starter motor for the flywheel.

Given that both will now need to be replaced, and I would like to stick with a lightweight flywheel, are you able to advise the right combination before I buy these please?

Thanks

Ian

[ianc]

Mark, apologies I didn’t read your post in full!

[Polarsilver]

With my Inertia Starter Motor ..Had similar issue with poor cranking to find i had a 10 tooth inertia starter gear ..this car still started with the 10 teeth starter but was lazy cranking.
Changed to a correct "Nine" tooth inertia gear and we are feeling much better.

Sure others on here will know more.

[mk1]

Hi Ian,

I kept adding to it.

As long as the two parts match, there isn't "that" much in it.

Inertia are more original, probably a benefit on an original S.
Pre-engaged work better, probably an advantage on a car that gets used.

Please see the last comment above taken from the MS web site about starters with the wrong number of teeth, this may also be a reason for your issue.

Hope this helps.

M

[ianc]

Mark

I’ve just checked the invoice from the mini specialist who changed the flywheel. It says “ST1 ultralight flywheel assembly inertia”

I know i’ve fitted an inertia starter.

Does anything else spring to mind.

[ianc]

Hi Polarsilver

Thanks for your reply

The starter I fitted had nine teeth, and I actually compared and counted the teeth against the original

Thanks

Ian

[mk1]

The issue with the tooth count on the starter springs to mind.

Or possibly the "inertia flywheel" that was supplied was labelled up wrong.

They REALLY are hard to tell apart.

[Peter Laidler]

Reading through this and having been there, you have to accept that there's only one thing that touches the ring gear on the flywheel - and that's the starter teeth. And there's only one thing that touches the cog-gears on the starter - and that's the ring gear on the flywheel . The problem can only be one or the other - or both! Mismatched is the obvious and most common. As they say, common problems occur commonly

[burchy35]

I had a similar problem. Its was because I made up a twin spring clutch set up which slightly moved the position of the flywheel and didn't line up with the starter properly.
I only noticed it when starting it and it kept jumping out.
Luckily I sorted it before the ring gear got too damaged.
Roy B

[indigo]

You can also purchase a pre-engaged starter to suit the 109 tooth ring gear.
For example the Minispares GXE1004 looks like a pre-engaged starter, however it is referred to as an inertia starter motor having 9 teeth.
The pinion on this starter would attack the ring gear on the opposite side to that of a normal inertia starter.

[iain1967s]

Tooth count and profile differences for the original inertia ‘bendix’ versus late pre-engaged.